The present invention relates to a phosphorous-containing flame retarding epoxy resin and their composition comprising the nitrogen-containing flame retarding epoxy resin. More specifically, the present invention relates to a flame retarding epoxy resin having a pendent phosphorous-containing functional group and their composition comprising the nitrogen-containing flame retarding epoxy resin.
Under the consideration of economics and productivity, an encapsulating material for currently semiconductor devices is mostly an epoxy-based resin composition. To insure the use safety, electronic parts for the semiconductor are required to meet a flame retarding specification regulated by the UL. The approach to attain the flame retarding specification is addition of halogen-containing epoxy resin and diantimony trioxide as a flame retarding assistant into epoxy resin compositions for encapsulating electronic parts. However, it is known that such flame retarding assistants are harmful to human and animal. For example, diantimony trioxide has been classified a cancerous material while an epoxy resin containing halogen such as bromine will produce corrosive bromine free radical and hydrogen bromide during burning. Also, an aryl compound containing high content bromine will produce toxic brominated furanes and brominated dioxins compounds. Such toxic materials have adverse effects to human, animal and environment. Thus, it is eagerly required to semiconductor manufacture for developing a novel epoxy resin without halogen neither diantimony trioxide to resolve the problems associated with the use of halogen-containing epoxy resin and diantimony trioxide.
For flame retarding resins, a phosphorous-containing compound is widely used as a new generation flame retarding agent. Among others, it commonly uses phosphorus or phosphorous-containing organic compound (e.g. triphenyl phosphate (TPP), tricresyl phosphate (TCP), and phosphoric acid etc.,) as a flame retarding agent instead of halogen-containing flame retarding agents to improve flame retarding characteristic of thermosetting resin. By using such a conventional phosphorous-containing compound as a flame retarding agent, it is required to incorporate such a flame retarding agent in a large amount into epoxy resin composition formulations due to its poor flame retardant effect. It will cause lowering of relative amount of the epoxy resin and the curing agent contained in the formulation so that the performances of the epoxy formulation will decrease. Moreover, since the conventional phosphorous-containing compound has low molecular weight and in turn exhibits a high migration, it will directly affect the characteristics of the resulting epoxy resin, e.g. electrical property and strength, etc., and will make it impracticable. For example, Taiwan Patent Publication No. 339353 discloses the use of red phosphorous in stead of halogen and antimony compound as a flame retarding agent. However, when the article prepared from the resin containing red phosphorous is boiled at an elevated temperature, the red phosphorous contained therein will be hydrolyzed resulting in hazardous operation and then affect adversely on the process and product.
Recently, under the considerations of environmental protection and safety, a reactive type resin flame retarding agent is used to substitute for currently used flame retarding agent, especially a phosphorous-containing flame retarding agent is used in stead of brominated epoxy resin. For example, Japanese Patent Unexamined Publication Hei 9-235449 discloses the use a phosphorous-containing epoxy resin in stead of halogen and antimony compound as a flame retarding agent. The patent publication claims that the composition having the phosphorous-containing epoxy resin has improved fire resistance and would not produce dioxine during burning. However, since such additive type and reactive type phosphorous-containing substances possess low phosphorous content, the composition containing such phosphorous-containing substance exhibits poor fire resistance. To attain desired flame retarding effect, it is required to incorporating such a flame retarding agent in a large amount into epoxy resin composition formulations. It will cause lowering of relative amount of the epoxy resin and the curing agent contained in the formulation so that the performances of the epoxy formulation will decrease.
To replace of a halogen-containing compound and antimony-containing compound, it has recently developed a nitrogen- or phosphorous-containing compound as flame retarding agent. Most commonly used nitrogen-containing compound includes, for example, melamine, DICY, triazine-containing cyanate, etc. The phosphorous-containing compound includes reactive type phosphorous-containing compound having reactive functional group, and non-reactive type phosphorous-containing compound. The reactive type phosphorous-containing compound possesses a better heat stability than the non-reactive type phosphorous-containing compound since the reactive functional group contained therein could react with the other components to form a bond between therein. Therefore, the reactive type phosphorous-containing compound becomes a developed main stream in the future.
The most commonly used reactive type phosphorous-containing compound is a straight chain phosphorous-containing compound. Such a straight chain phosphorous-containing compound have a group of xe2x80x94Oxe2x80x94Pxe2x80x94Oxe2x80x94 in the main chain, it exhibits poor fire resistance than the flame retarding agent with or without containing halogen. Also, the straight chain reactive type phosphorous-containing compound or non-reactive type phosphorous-containing compound has poor processing ability.
To overcome the disadvantages associated with the current semiconductor encapsulating technique, the present inventors have investigated on epoxy resin and then developed a modified phosphorous-containing epoxy resin. Thus the present invention is completed.
The present invention relates to a phosphorous-containing flame retarding epoxy resin and their composition comprising the nitrogen-containing flame retarding epoxy resin. More specifically, the present invention relates to a flame retarding epoxy resin having a pendent phosphorous-containing functional group and their composition comprising the nitrogen-containing flame retarding epoxy resin.
The present invention relates to a phosphorous-containing epoxy resin of the following formula: 
wherein R represents a C1-6 alkylene group;
a represents an integral number of from 1 to 10;
b represents an integral number of from 0 to 10;
X represents a group of formula xe2x80x94(Oxe2x80x94CH2xe2x80x94CH(OH)xe2x80x94CH2-Oxe2x80x94Mxe2x80x94)yxe2x80x94, in which y represents an integral number of from 0 to 20; and M represents a group selected from the following groups (E1)xe2x96xa1(E2), and (E3): 
wherein R3 represents a C1-6 alkyl group; A represents a chemical bond, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, C1-6 alkylene group, or a group of the following formula: 
wherein R1 represents a hydrogen atom or a C1-6 alkyl group, d represents an integral number of from 0 to 6, R2s are the same or different and represent a hydrogen atom or a group of the following formula: 
in which R1 is the same as defined above; 
in which R1 is the same as defined above; m and n are the same or different and represent an integral number of from 0 to 3;
Ar1 and Ar2 are the same or different and represent a group selected from the following formulae (E3) or (E4): 
wherein R1, m, and n are the same as defined above.
The phosphorous-containing epoxy resin of the present invention is obtained from the steps of addition reacting a phosphorous-containing compound having the following formula: 
(in which Hal represents a halogen atom, e.g. fluorine, chlorine, bromine, or iodine, etc.) with aldehydes having reactive functional group, then condensing reacting with phenols, and finally reacting with epihalohydrins.
As the phosphorous atom is located on the side chain of the phosphorous-containing epoxy resin of the present invention, the difference between the phosphorous-containing epoxy resin of the present invention and an epoxy resin is lowered when the phosphorous-containing epoxy resin is directly added into an epoxy resin composition. Thus, the processing problem associated with the halogen-containing epoxy resin will be overcome. Moreover, since the side chain molecular will decrease the flow ability of the phosphorous-containing epoxy resin of the present invention, the epoxy resin exhibit high stability at an elevated temperature which will result in more excellent heat resistance. The phosphorous-containing epoxy resin of the present invention has excellent flame retardant effect and heat resistance, it is therefore useful as an encapsulating material for semiconductor and imparts the encapsulated article with excellent flame retardant effect and heat resistance. Further, the phosphorous -containing epoxy resin of the present invention is also useful as a flame retarding agent or stabilizer for resin other than epoxy resin, such as thermosetting and thermoplastic resin and is useful for producing various electronic products.
The term xe2x80x9cC1-6 alkyl groupxe2x80x9d used herein means a liner or branched alkyl group having 1 to 6 carbon atoms, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, s-butyl, t-butyl, n-pentyl, isopentyl, n-hexyl and isohexyl and the like.
The term xe2x80x9cC1-6 alkylene groupxe2x80x9d used herein means a residue obtained by subtracting two hydrogens atom from a linear or branched alkane having 1 to 6 carbon atoms.
The flame retarding phosphorous-containing epoxy resin of the present invention has a high nitrogen content thus possesses excellent flame retarding effect and heat resistance, it therefore can be used as an epoxy resin for producing semiconductor encapsulating material. It can also be incorporated into other thermosetting and thermoplastic resin material to produce various electronic products.
Accordingly, the present invention also relates to a use of the flame retarding phosphorous-containing epoxy resin of the present invention as a flame retarding agent in either thermosetting or thermoplastic resin.
Examples of the thermosetting resin in which the flame retarding phosphorous-containing epoxy resin of the present invention is suitable include, such as, epoxy resin and novolac resin, and the like. Examples of the thermoplastic resin in which the flame retarding phosphorous-containing epoxy resin of the present invention is suitable include, such as, polystyrene, polypropylne, polyterephthalate, polycarbonate, polystyrene, styrene-butadiene-styrene copolymer, acrylonitrile-butadiene-styrene copolymer, polyamide, polyimide, polysulfone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and the like.
The present invention further relates to a flame retarding epoxy resin composition, which comprises the flame retarding phosphorous-containing epoxy resin of the present invention, a curing agent containing reactive hydrogen capable to react with an epoxy group, and a curing promoter.
The curing agent containing reactive hydrogen capable to react with an epoxy group used in the flame retarding epoxy resin composition, hereinafter referred to xe2x80x9cthe curing agentxe2x80x9d, can be various halogen-free curing agent, and includes bisphenol resin, polyhydroxy phenol resin, phenolic resin, and anhydride, and the like.
Examples of the bisphenol resin include compound of the formula HOxe2x80x94Phxe2x80x94Zxe2x80x94Phxe2x80x94OH (wherein Ph represents a phenylene group, Z=a chemical bond, xe2x80x94CH2xe2x80x94C(CH3)2xe2x80x94, xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94COxe2x80x94 or xe2x80x94SO2xe2x80x94). Embodiments of the bisphenol resin include, but not limited to, tetramethylbisphenol AD, tetramethylbisphenol S, 4,4xe2x80x2-biphenol, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenol, or 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-4,4xe2x80x2-biphenol, and the like.
Examples of the polyhydroxy phenol resin include, but not limited to, tris(4-hydroxyphenyl)methane, tris(4-hydroxyphenyl)ethane, tris(4-hydroxyphenyl)propane, tris(4-hydroxyphenyl)butane, tris(3-methyl-4-hydroxyphenyl)methane, tris(3,5-dimethyl-4-hydroxyphenyl)methane, tetrakis(4-hydroxyphenyl)methane, tetrakis(3,5-dimethyl-4-hydroxyphenyl)methane, and the like.
Examples of the phenolic resin include phenol-formaldehyde condensate, cresol-phenolic condensate, bisphenol A-phenolic condensate and dicyclopentadiene-phenolic condensate, and the like.
Examples of the anhydrides include, such as 3,3xe2x80x2,4,4xe2x80x2-benzophenone-tetracarboxylic anhydride (BTDA), trimetallitic acid trianhydride (BTDA) and pyromellitic acid dianhydride, and the like.
The curing agent used in the flame retarding epoxy resin composition of the present invention can be a nitrogen- and phosphorus-containing curing agent of the following formula (II): 
wherein R4 represents xe2x80x94NHR5, a C1-6 alkyl group, or a C6-10 aryl group which may further substituted with one or more substitutents selected from the group consisting of hydroxyl, amino, carboxy, and C1-6 alkyl group;
R5 represents a hydrogen atom, xe2x80x94(CH2xe2x80x94R6)cxe2x80x94H or a group of the following formula (5): 
wherein R6 represents a phenylene group, or a naphthalene group optionally substituted with one or more substitutents selected from the group consisting of hydroxyl, amino, carboxy, and C1-6 alkyl group or represents the group of the following formula-: 
[wherein R3 represents a C1-6 alkyl group; A represents xe2x80x94Oxe2x80x94, xe2x80x94Sxe2x80x94, xe2x80x94SO2xe2x80x94, xe2x80x94COxe2x80x94, xe2x80x94CH2xe2x80x94, xe2x80x94C(CH3)2xe2x80x94, or the group of the following group: 
and
c represents an integral number of from 0 to 20;
provided that at least one R5 is not a hydrogen atom.
The term xe2x80x9caryl groupxe2x80x9d used herein includes phenyl group and naphthyl group.
Examples of the curing promoter used in the flame retarding epoxy resin composition of the present invention include tertiary amine, tertiary phosphine, quaternary ammonium salt, phosphornium salt, boron trifluoride complex, lithium compound or imidazole compound, or a combination thereof.
Examples of the tertiary amine include trimethylamine, triethylamine, diisopropyl ethylamine, dimethyl ethanolamine, dimethylaniline, tris(N,N-dimethylaminomethyl)phenol, or N,N-dimethylaminemethylphenol, and the like.
Examples of the tertiary phosphine include triphenylphosphine.
Examples of the quaternary ammonium salt include tetramethylammonium chloride, tetramethylammonium bromide, triethylbenzylammonium chloride, triethylbenzylammonium bromide, or triethylbenzylammonium iodide, and the like.
Examples of the phosphornium salt include tetrabutylphosphornium chloride, tetrabutylphosphornium bromide, tetrabutylphosphornium iodide, tetrabutylphosphate acetate complex, tetraphenylphosphornium chloride, tetraphenylphosphornium bromide, tetraphenylphosphornium iodide, ethyltriphenylphosphornium chloride, ethyltriphenylphosphornium bromide, ethyltriphenylphosphornium iodide, ethyltriphenylphosphate acetate complex, ethyltriphenylphosphate phosphate complex, propyltriphenylphosphornium chloride, propyltriphenylphosphornium bromide, propyltriphenylphosphornium iodide, butyltriphenylphosphornium chloride, butyltriphenylphosphornium bromide, and butyltriphenylphosphornium iodide, and the like.
These curimg promoter can be used along or in a combination thereof
The flame retarding epoxy resin composition of the present invention, in addition to the flame retarding nitrogen-containing epoxy resin of the present invention, can also comprise other conventional epoxy resin. Examples of the conventional resin include, for example, bisphenol glycidyl ether, bis(diphenol) glycidyl ether, resorcinol glycidyl ether, glycidyl ether of a nitrogen-containing ring, glycidyl ether of dihydroxynaphthalene, phenolic polyglycidyl ether, and polyhydroxy phenol polyglycidyl ether, and the like.
Examples of the bisphenol glycidyl ether include, for example, bisphenol A glycidyl ether, bisphenol F glycidyl ether, bisphenol AD glycidyl ether, bisphenol S glycidyl ether, tetramethyl-bisphenol AD glycidyl ether, and tetramethyl-bisphenol AD glycidyl ether, etc.
Examples of the bis(diphenol) glycidyl ether include, for example, 4,4xe2x80x2-biphenol glycidyl ether, 3,3xe2x80x2-dimethyl-4,4xe2x80x2-biphenol glycidyl ether, and 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-4,4xe2x80x2-biphenol glycidyl ether, etc.
Examples of the phenolic polyglycidyl ether include, for example, phenolic polyglycidyl ether, cresol-phenolic polyglycidyl ether, and bisphenol A-phenolic polyglycidyl ether, etc.
Examples of the polyhydroxy phenol polyglycidyl ether include, for example, tris(4-hydroxyphenyl)methane polyglycidyl ether, tris(4-hydroxyphenyl)ethane polyglycidyl ether, tris(4-hydroxyphenyl)propane polyglycidyl ether, tris(4-hydroxyphenyl)butane polyglycidyl ether, tris(3-methyl-4-hydroxyphenyl)methane polyglycidyl ether, tris(3,5-dimethyl-4-hydroxyphenyl)methane polyglycidyl ether, tetrakis(4-hydroxyphenyl) ethane polyglycidyl ether, tetrakis(3,5-dimethyl-4-hydroxyphenyl)ethane polyglycidyl ether, dicyclopentene-phenolic polyglycidyl ether, and a mixture thereof.
Examples of the glycidyl ether of a nitrogen-containing ring include, for example, glycidyl ether of isocyuric acid and glycidyl ether of isocyurate.
Examples of the glycidyl ether of dihydroxy-naphthalene include, for example, 1,6-dihydroxynaphthalene diglycidyl ether and 2,6-dihydroxynaphthalene diglycidyl ether.
These epoxy resins can be used alone or in a mixture thereof in the phosphorous-containing epoxy resin composition of the present invention. Among them, bisphenol A glycidyl ether, phenolic polyglycidyl ether, tris(4-hydroxyphenyl)methane polyglycidyl ether, dicyclopentene-phenolic polyglycidyl ether, tetrakis(4-hydroxyphenyl)ethane polyglycidyl ether, or a mixture thereof is preferable.
When the flame retarding epoxy resin composition of the present invention contains both the flame retarding phosphorous-containing epoxy resin of the present invention and conventional epoxy resin, the weight ratio of the flame retarding phosphorous-containing epoxy resin of the present invention to the conventional epoxy resin is (3-100):(97-0), preferably (10-80):(90-20). If the amount of the flame retarding phosphorous-containing epoxy resin of the present invention is less than 3% by weight, a retarding property and a heat resistance of an article prepared from the resin composition of the present invention are insufficient.
In the flame retarding epoxy resin composition of the present invention, the amount of the curing agent depends on the epoxy equivalent of the used epoxy resin and the active hydrogen equivalent of the curing agent. Generally, the ratio of the epoxy equivalent of the epoxy resin to the active hydrogen equivalent of the curung agent is from 1:0.5 to 1:1.5, preferably from 1:0.6 to 1:1.4, more preferably from 1:0.7to 1:1.3.
In the flame retarding epoxy resin composition of the present invention, the amount of the curing promoter is from 0.01 to 5% by weight, preferably from 0.05 to 3% by weight, relative to the total weight of the flame retarding epoxy resin composition of the present invention. If the amount of the curing promoter is more than 5% by weight, although it causes shorten reaction time, it easily produces byproduct, which adversely affects the electronic property, moisture resistance, water absorbability in the final use. If the amount is less than 0.01% by weight, the reaction rate is too low so that the production is decreased.
The amount of the curing promoter also depends on a gelling time and viscosity of the flame retarding epoxy resin composition of the present invention. Generally, the curing promoter is added in an amount that controls the gelling time of the flame retarding epoxy resin composition of the present invention in the range of 30 to 500 sec/171xe2x96xa1, and the viscosity of the flame retarding epoxy resin composition of the present invention in the range of 20 to 500 cps/25xe2x96xa1.
The flame retarding epoxy resin composition of the present invention further comprises other additives, for example, such as inorganic filler, coupling agent, pigment (e.g. carbon black and ferrous oxide), molding release agent and low stress additives.
Examples of the inorganic filler suitably used in the flame retarding epoxy resin composition of the present invention include sphere type and cornered type molten silica, crystalline silica, and the like, and quartz glass powder, talc powder, alumina powder, zinc borate, aluminum hydroxide, magnesium hydroxide, calcium carbonate, aluminum nitride, and the like. These filler can be used alone or in a combination thereof. With the cornered type molten silica, crystalline silica, and a mixture of the cornered type molten silica and crystalline silica are preferred.
An average particle size of these inorganic filler is preferably from 1 to 30 microns. If the average particle size is less than 1 micron, it will cause the increasing viscosity and decreasing flow ability of the resin composition. If the average particle size is more than 30 micron, it will cause uneven dispersion of the resin and of the filler in the epoxy resin composition, which will in turn cause resin overflowing during encapsulating application and affect physical property of the cured article. Additionally, the maximum particle size is preferably less than 150 microns to avoid causing a narrow casting channel or poor filling of voids.
The amount of the inorganic filler is from 60 to 92% by weight, preferably from 65 to 90% by weight based on the total weight of the flame retarding epoxy resin composition of the present invention. If the amount of the inorganic filler is less than 60% by weight, the relative ratio of the epoxy resin in the resin composition will be increased so that an overflowing of the resin easily occurs during encapsulating. If the amount of the inorganic filler is more than 92% by weight, a viscosity of the resin composition will increase and result in the decrease of flow ability.
The present invention will further illustrate by reference to the following synthesis examples, working examples, and comparative examples. However, these synthesis examples and working examples are not intended to be limiting of the scope of the present invention.
The epoxy equivalent weight (EEW), the viscosity, and a soften point used herein are determined according to the following methods:
(1) Epoxy Equivalent Weight (EEW): The epoxy equivalent weight (EEW) is determined according to the method of ASTM 1652, the epoxy resin to be tested is dissolved in a mixture solvent of chlorobenzene:chloroform in a weight ratio of 1:1, the resultant mixture is titrated with HBr/glacial acid by using crystalline violet as an indicator.
(2) Viscosity: The viscosity is determined by placing the epoxy resin to be tested in a thermostat maintaining at 25xe2x96xa1 for 4 hours and measuring the viscosity by using Brookfield Viscosmeter at 25xe2x96xa1.
(3) Soften point: The soften point is determined by applying the epoxy resin to be tested on an O-ring, placing a ball on the applied epoxy resin, gradually heating the epoxy resin, and measuring the temperature when the ball falls into the O-ring.
Each ingredient used in these synthesis examples, working examples, and comparative examples are illustrated as follows.
Epoxy resin A: polyglycidyl ether of cresol-phenolic condensate having an epoxy equivalent weight of 200 to 220 gram/equivalent and a hydrolyzable chlorine of below 200 ppm, under trade name of CNE 200ELB sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan, R.O.C.
Epoxy resin B: 3,3xe2x80x2,5,5xe2x80x2-tetramethyl-4,4xe2x80x2-biphenol having an epoxy equivalent weight of 180 to 195 grams/equivalent, under trade name of YX4000H sold and manufactured by Yuka Shell Epoxy Co. Ltd., Japan.
Epoxy resin C: a diglycidyl ether of tetrabromobisphenol A having an epoxy equivalent weight of 330 to 350 grams/equivalent, under trade name of BEB350 sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan, R.O.C.
Curing agent A: a curing agent having reactive hydrogen of 105 to 110 grams/equivalent, under trade name of PF-5110 sold and manufactured by Chang Chun Plastic Co., Ltd., Taiwan, R.O.C.
Curing agent B: a nitrogen- and phosphorus-containing curing agent prepared from the following Synthesis Example 3.
Curing promoter A: triphenylphosphine.
Curing promoter B: 2-methylimidazole (hereinafter referred to 2MI).